Denon AVR 3300: Cross-talk between inputs

Guest

I've got a Denon receiver (AVR 3300, circa December 1999) and have a Denon CD changer connected to the digital coax input. I have line-level audio from my TV connected to one of the analog inputs on the 3300 (TV/DBS). To listen to the CD, I hit the "CD" button (8) on the 3300's remote, and to listen to TV I hit 4 (TV/DBS).

If I have the CD changer playing a CD, and I select the TV/DBS source, I can hear the audio from the CD and the TV at the same time in the speakers (although the CD audio is fainter and sounds distorted / noisy). When I select the CD as the source, I hear the CD audio just fine, with no hint of the audio from the TV/DBS source.